I was a little snarky about Walmart's new effort when I wrote about it last week but didn't have a chance to really dig into the meat of the new index. Joel (with some reporting help from Marc Gunther (no relation), Preston Gralla, Catherine Greener (awesome name), and the GreenBiz.com news staff) cuts through the fluff and finds a lot to be cautiously excited about.

Some of the key takeaways:

• The new system rates companies, not products, from their answers to 15 questions Walmart provided.

• The questions are bundled into four categories -- energy and climate, material efficiency, natural resources, and people and community.

• Walmart has actually been working on this index on their in-house brands for over a year.

• Walmart will factor in a company's rating in the index when they are making purchasing decisions but will remain focused on low prices as their main consideration.

Joel thinks this is a good start but that Walmart still has a long way to go. He wrote:

Do such shortcomings render the Walmart Sustainability Index as greenwash? No. This is a solid first effort. It's important to note that over the past year, Walmart engaged some 20 universities, a handful of environmental activist groups, associations like Business for Social Responsibility, many of its key suppliers, and a small army of consultants. Patagonia's iconoclastic founder, Yvon Chounaird, has played a role. It's gone through a great deal of thinking and more than a few iterations. (You can download a backgrounder on a slightly earlier iteration of the Index here -- PDF, that contained 16 questions.) This was not some slap-dash effort.

Shea Gunther is a podcaster, writer, and entrepreneur living in Portland, Maine. He hosts the popular podcast "Marijuana Today Daily" and was a founder of Renewable Choice Energy, the country's leading provider of wind credits and Green Options. He plays a lot of ultimate frisbee and loves bad jokes.